Or one of these?
Ahha! Figured out the upload! This first one is the allen one that I can't get broken loose, where I think I need to fill at.
Or one of these?
Fill screw A is where you add fluid.
You don't need to mess with the allen screw, there is a special tool to remove the head of the hydraulic cylinder or you can get it out with a pipe wrench if you are very careful but it will scuff it up pretty bad. The piston cap (probably wrong teminology) screws out and then the piston comes out.
This is definitely a job left to a pro.
Thanks for your help Carolina! I'm just going to top off the fluid for now with some of the Trans X stuff and see if that stops the leak.